Saint Charles, South Dakota Weather Forecast Discussion

402
FXUS63 KFSD 301910
AFDFSD
Area Forecast Discussion
National Weather Service Sioux Falls SD
210 PM CDT Tue Sep 30 2025
.KEY MESSAGES...
- Well above normal temperatures will continue into the
  upcoming weekend. A few record high temperatures and warm low
  temperatures may be possible this week.
- Isolated to very scattered sprinkles to showers will be
  possible Wednesday and Thursday morning. Most will not see
  rain however.
- Dry and occasionally breezy afternoon conditions could lead
  to low end fire weather concerns as fire fuels continue to dry
  out. One period of higher concern will develop Friday into
  Saturday.
- Rain chances continue to focus on Saturday night into Sunday.
  Probabilities of rain have increased slightly, but there
  remains considerable uncertainty on the coverage of rainfall.
&&
.DISCUSSION...
Issued at 207 PM CDT Tue Sep 30 2025
THIS AFTERNOON: Considerable high level cloud cover continues this
afternoon as the region falls into an area of southwesterly mid-lvl
flow and on the southern periphery of a weak 60 knot upper jet. A
wave pivoting through central Nebraska will shift this upper jet
eastward tonight and push the cirrus shield further east as well.
Temperatures remain slightly cooler today with the cloud cover, but
are still expected to reach the upper 70s to lower 80s.
TONIGHT: Persistent southerly winds continue overnight, keeping
temperatures warmer than normal throughout the Tri-State area.  By
midnight we`ll begin to see signs of increased moisture convergence
and warm air advection in the form of mid-lvl clouds over areas
along and west of the James River valley. Persistent but focused
lift in a narrow corridor may lead to the development of scattered
showers. Around 100-200 J/KG MUCAPE could also result in an isolated
lightning strike or two within high based activity.
WEDNESDAY:  Isolated to scattered showers may continue to drift
eastward slowly on Wednesday, with the area of mid-lvl moisture and
very weak dPVA shifting into western Minnesota and Iowa in the
afternoon.  While most of this activity may wane by mid-day, there
are several CAMs that redevelop the lingering mid-lvl ACCAS field
into showers and isolated thunderstorms by late evening over
southern Minnesota and northern Iowa.   Temperatures will rise a few
degrees on Wednesday, but cloud cover may prevent a much higher
climb.  The breezy to occasionally gusty winds will continue an
elevated fire danger risk mostly along and west of I-29 in the
afternoon, though critical conditions are not expected.
THURSDAY: Shortwave energy moves east of the area Thursday, with mid-
lvl heights rising through the Plains.  Low-lvl temperatures begin
to rise through out the Plains under these rising heights, with
highs climbing into the middle to upper 80s in most areas.
Winds though will be weaker though given the influence of a
stalled frontal boundary in the area.
FRIDAY:  Model agreement continues to grow that we`ll see a very
warm day on Friday as the aforementioned warm front surges into
North Dakota and northwest Minnesota.  Sharp southerly low-lvl and
boundary layer flow will promote strong mixing and sharp rises in
afternoon high temperatures in the afternoon.  A few record high
temperatures will be possible and have increased temperatures
slightly over populated NBM guidance. As surface cyclogenesis
develops over the western Dakotas, we`ll begin to see a tightening
SPG further east over the Tri-State area.  This should result in
increasing sustained winds but also potential for some very gusty
winds (25 to 35 mph) through the night and persistent mixing.  Low
temperatures in most areas may fail to fall out of the 60s.
Fire weather conditions will deteriorate slightly on Friday
afternoon with the warm and dry airmass in place. However, while
the hot dry windy index suggest over an 80% probability of
exceeding the 90th percentile conditions, wonder if this isn`t
being biased a bit by the stronger evening/overnight wind
potential (which falls outside the lowest RH drops).
SATURDAY-MONDAY: A surface front will start the day Saturday
sprawled from northwestern Nebraska through central South Dakota and
into northwest Minnesota at daybreak. With a continued slowdown of
mid-lvl troughing moving into the Rockies, this will mean that the
front remains nearly stationary through much of the day.  As a
result, expected a very warm and very windy day throughout the
region. GFS/ECMWF and their ensembles both suggest that winds will
fall well out of climatology and raw gusts from both models suggest
gusts between 30 and 45 mph may develop from daybreak Saturday into
Saturday night. Thus, have blended in a higher amount of NBM 90th
percentile data over that 18 hour time frame, and further upwards
adjustments may be needed. Temperatures Saturday again rise into the
upper 80s to lower 90s, so those with outdoor activities will need
to stay aware of the increased heat potential.
There still remains some modest agreement in medium range models
with the track and intensity of the mid-lvl shortwave exiting the
Rockies this weekend.  The latest ECMWF has trended towards the GFS
bringing a compact wave through the Nebraska panhandled through
central and northeastern South Dakota.  This system likely pushes a
cold front eastward Saturday  night into Sunday, but despite more
widespread QPF in the GFS both medium range models show fairly
strong capping ahead of the boundary.  If precipitation can`t
develop along the front, then the greatest rain risks may shift
northwest of the CWA into the deformation band of the system. Still
plenty of time to watch trends on this one, though overall
instability remains low so severe weather risks should remain very
low.  The front passes southeast early Sunday and with high pressure
moving into the Northern Plains, the rain chance likely diminishes
quickly. The latest NBM may again be too spread out with PoPs into
Sunday and Monday.  Higher confidence in a brief but sharp cooldown
in temperatures towards the 60s to start next week.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1152 AM CDT Tue Sep 30 2025
VFR conditions will continue through the overnight hours as a
thick high level cloud base moves through. A few 5-7K ft CU may
develop this afternoon, as winds increase slightly from the
south.
Overnight, ceilings may gradually lower with scattered high base
showers possible in a narrow corridor along or west of I-29
through daybreak. VFR conditions remain likely through
Wednesday morning with southeasterly flow turning gusty from the
south late in the morning.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
DISCUSSION...Dux
AVIATION...Dux

NWS FSD Office Area Forecast Discussion